Easiest way to load splash into main_image on page load?

I'd like to have some sort of "welcome to the gallery, click on the thumbs below to start" image as a splash when navigating to the gallery page.  I don't want it listed in the thumbs so the class=active isn't what I'm looking for.  I can think of a few ways to do it in js but I'd like to know if anyone knows a clean, simple way to do it.

Thanks in advance